probe_eddy_current: Support TAP_THRESHOLD parameter on "tap" probes

Allow the "tap_threshold" to be overriden during PROBE type commands.
This makes it easier to calibrate an initial tap_threshold.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Config_Reference.md

@@ -2326,9 +2326,16 @@ sensor_type: ldc1612
 #samples_tolerance:
 #samples_tolerance_retries:
 #   See the "probe" section for information on these parameters.
-#tap_threshold: 0
-#   Noise cutoff/stop trigger threshold delta Hz per sample
-#   See the Eddy_Probe.md for explanation
+#tap_threshold:
+#   Noise cutoff/stop trigger threshold (in Hz). Specify this value to
+#   enable support for "METHOD=tap" probe commands. See Eddy_Probe.md
+#   for more information. Larger values make the tap detection less
+#   sensitive. That is, larger values make it less likely the toolhead
+#   will incorrectly stop early due to noise, while increasing the
+#   risk of the toolhead not correctly stopping when it first contacts
+#   the bed. If this value is specified then one may override its
+#   value at run-time using the "TAP_THRESHOLD" parameter on probe
+#   commands. The default is to not enable support for "tap" probing.
 ```
 
 ### [axis_twist_compensation]

docs/Eddy_Probe.md

@@ -123,7 +123,6 @@ and that upon collision it always decreases by at least this value.
 #samples: 3
 #samples_tolerance: 0.025
 #samples_tolerance_retries: 3
-tap_threshold: 0 # 0 means tap is disabled
 ```
 
 Before setting it to any other value, it is necessary to install `scipy`:

docs/G-Codes.md

@@ -1247,6 +1247,9 @@ additional parameters if a `[probe_eddy_current]` section is defined:
   using `METHOD=rapid_scan` this specifies the measurement time window
   at each target. If not specified, the default is 0.100 (which is
   100ms).
+- `TAP_THRESHOLD=<value>`: This overrides the `tap_threshold`
+  specified in the `[probe_eddy_current]` config section when probing
+  using `METHOD=tap`.
 
 #### PROBE_EDDY_CURRENT_CALIBRATE
 `PROBE_EDDY_CURRENT_CALIBRATE CHIP=<config_name>`: This starts a tool

klippy/extras/probe_eddy_current.py

@@ -486,7 +486,7 @@ class EddyTap:
         self._z_min_position = probe.lookup_minimum_z(config)
         self._gather = None
         self._filter_design = None
-        self._tap_threshold = config.getfloat('tap_threshold', 0., minval=0.)
+        self._tap_threshold = config.getfloat('tap_threshold', 0., above=0.)
         if self._tap_threshold:
             self._setup_tap()
     # Setup for "tap" probe request
@@ -503,7 +503,7 @@ class EddyTap:
         mcu = self._sensor_helper.get_mcu()
         sos_filter = trigger_analog.MCU_SosFilter(mcu, cmd_queue, 5)
         self._trigger_analog.setup_sos_filter(sos_filter)
-    def _prep_trigger_analog_tap(self):
+    def _prep_trigger_analog_tap(self, gcmd):
         if not self._tap_threshold:
             raise self._printer.command_error("Tap not configured")
         sos_filter = self._trigger_analog.get_sos_filter()
@@ -511,7 +511,9 @@ class EddyTap:
         sos_filter.set_offset_scale(0, 1., auto_offset=True)
         self._trigger_analog.set_raw_range(0, MAX_VALID_RAW_VALUE)
         convert_frequency = self._sensor_helper.convert_frequency
-        raw_threshold = convert_frequency(self._tap_threshold)
+        tap_threshold = gcmd.get_float("TAP_THRESHOLD",
+                                       self._tap_threshold, above=0.)
+        raw_threshold = convert_frequency(tap_threshold)
         self._trigger_analog.set_trigger('diff_peak_gt', raw_threshold)
     # Measurement analysis to determine "tap" position
     def _validate_samples_time(self, measures, start_time, end_time):
@@ -572,7 +574,7 @@ class EddyTap:
                                         trig_pos[0], trig_pos[1], trig_pos[2])
     # Probe session interface
     def start_probe_session(self, gcmd):
-        self._prep_trigger_analog_tap()
+        self._prep_trigger_analog_tap(gcmd)
         self._gather = EddyGatherSamples(self._printer, self._sensor_helper)
         return self
     def run_probe(self, gcmd):